Are there any disadvantages to adding a toilet so that the toilet waste drains into the washing machine drain? We have a small home and it only has one toilet. There are four people who live here so we are looking to maximize our space by adding a toilet in the garage. Is this possible? Any pitfalls?
It depends what the size of the drain going to the washing machine is. As mentioned it should be put through your local authority but if your drainage under the washing machine is accessible and at least 3" it is possible. Running the toilet straight into the wash machine drain isn't possible if it discharges through a floor waste (gully).